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SUMMARY: The aim of the study was to determine the number and anatomical configuration of roots and root canals of maxillary first and second premolars using cone-beam computed tomography scans. n273 CBCT scans were evaluated, obtaining a sample of 592 maxillary premolars. Root number and root canal anatomy were categorized using Ahmed´s classification. Data was analyzed using Pearson's Chi-squared test. Two roots were present on 157 first premolars, one root in 132 premolars and three roots in 17. Second premolars presented one root in 266 samples and two roots in 20; no second premolars presented three roots. Eight different configurations were found; the most frequent was 2MP B1 P1 in first premolars (51,3 %) and 1MP1 (63.6 %) in second premolars. The most frequent morphology found in maxillary premolars in Chilean population was two and three roots. The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals, generally of low to medium complexity, similar to what is found in other ethnic groups.

RESUMEN: El objetivo de este estudio fue determinar el número y la configuración de raíces y canales radiculares de primeros y segundos premolares maxilares utilizado tomografía computacional de haz cónico. 273 TCHC fueron evaluados, obtenido una muestra de 592 premolares maxilares. El número de raíces y la anatomía de los canales radiculares fueron categorizados utilizando la clasificación de Ahmed. Los datos fueron analizados con la prueba Chi- Cuadrado de Pearson. Dos raíces fueron observadas en 157 primeros presentaron una raíz en 266 muestras y dos raíces en 20; no se encontraron tres raíces en segundos premolares. Ocho diferentes configuraciones fueron encontradas; siendo la más frecuente 2MP B1 P1 en primeros premolares (51,3 %) y 1MP1 (63,6 %) en segundos premolares. La morfología radicular más frecuentemente encontrada en premolares de población Chilena fue de dos y tres raíces. El análisis de la anatomía interna usando TCHC mostró una gran variabilidad de en la distribución de los canales radiculares. Generalmente de mediana y baja complejidad como los encontrados en otros grupos etnicos.

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BACKGROUND: The aim of the study was to assess the number and anatomical classification of roots and root canals of first and second mandibular molars using cone-beam computed tomography (CBCT) in a Chilean population. MATERIALS AND METHODS: This study evaluated the CBCT scans of 289 patients aged between 14 and 86 years, obtaining a sample of 1022 mandibular first and second molars. The number of roots and root canals was evaluated according to the anatomical classification proposed by Ahmed in 2016. Data were analysed using Pearson's chi-squared test and ANOVA. RESULTS: Nine hundred fifty-one (93.05%) molars had two roots, while the remaining 71 (6.95%) molars had one root. The most frequent root and root canal morphologies found were: ²MM M² D¹ (29.65%), ²MM M²â»¹ D¹ (22.3%) and ²MM M¹ D¹ (13.4%) (M - mesial, D - distal), with a total of 32 different anatomical distributions. C-shaped canals were present in 56 molars and were more frequently found in women than in men (7.1% vs. 3.88%; p = 0.024). CONCLUSIONS: The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals. The most frequent morphology found in mandibular molars in a Chilean population was two roots and three canals.

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The aim of this prospective study was to determine the antibiotic bioavailability of a prophylactic protocol in patients undergoing third molar surgery. Samples from 25 patients were analysed (average age 21 ± 3.89 years, range 18-33 years; 14 female). The patients received single-dose prophylaxis of 2 g amoxicillin orally 1 hour prior to third molar surgery. Venous blood (1.5 ml) and blood from the third molar socket (1.50 ml) were obtained. The amoxicillin plasma concentration was determined in both samples by high performance liquid chromatography with a diode-array detector (HPLC/DAD). Their associations with demographic variables (age, height, weight, body mass index (BMI), sex) and antibiotic exposure time were analyzed using linear regression models. The mean amoxicillin plasma level detected in the venous blood was 1.21 ± 1.17 µg/ml (range 0.49-6.34 µg/ml) and in the third molar socket was 4.14 ± 2.24 µg/ml (range 0.86-7.46 µg/ml) (P < 0.001). No relationship was observed between the bioavailability of the drug and the patient biometric indices evaluated. The prophylactic administration of 2 g amoxicillin in third molar surgery showed greater bioavailability in the molar socket than the concentrations established as necessary to inhibit the growth of microorganisms that cause oral infections. The results show the need to review the current infection control protocols in oral surgery in light of the overestimated doses observed.

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The aim of this study was to assess the morphology of the mesial root canal system of maxillary molars and the frequency of MB2 canals using cone-beam computed tomography (CBCT). A total of 1374 teeth, first maxillary (1MS, n= 802) and second maxillary molars (2SM, n= 572) of 508 Chilean patients between 8 to 77 years were evaluated through CBCT. The mesiobuccal root was evaluated in all three thirds. Root canal morphology was classified according to Vertucci's method. Data were analyzed by Pearson's Chi-square and Cuzick trend tests. MB2 canal frequency in 1MS was 73.44% and in 2MS 42.48%. The most frequent morphology in 1MS and 2MS were Vertucci type II and I, respectively. No statistically significant association was found between frequencies and side or according to gender (P>0.05). A positive association was found as the age increased in both 1MS and 2MS (P<0.001 and P= 0.023, respectively). Given the anatomical complexity of the mesiobuccal root and the frequent presence of the MB2 canal, the clinician must assume the existence of two canals in this root. CBCT scanning is a good way to initially identify this canal in the different root thirds.

Determinar la morfología del sistema de canales de la raíz mesial de molares maxilares y la frecuencia del canal MB2 usando tomografía computadorizada de haz cónico (TCHC). Un total de 1374 dientes, primeros molares maxilares (1MS, n= 802) y segundos molares maxilares (2MS, n= 572) de 508 pacientes Chilenos entre 8 y 77 años fueron evaluados a través de la TCHC. Se evaluó la raíz mesiobucal en todos sus tercio. La clasificación de Vertucci fue utilizada para determinar la morfología del sistema de canales. Los datos fueron analizados con los test Chi-Cuadrado de Pearson y la prueba de tendencia de Cuzick. La frecuencia del canal MB2 para el 1MS fue 73,44% y el 2MS 42,48%. La morfología mas frecuente en el 1MS y 2MS fueron el tipo II y I de Vertucci, respectivamente. No se encontró asociación significativa entre la frecuencia y el lado o sexo (p>0,005). Una asociación positive fue encontrada a medida que aumentaba la edad en ambos 1MS y 2MS (p<0,001 y p= 0,023, respectivamente). Dada la complejidad de la anatomía de la raíz mesiobucal y la frecuente presencia del canal MB2, el clínico debe asumir la existencia de dos canales en esta raíz. La TCHC es una buena manera de identificar tempranamente el canal en los diferentes tercio radiculares.

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Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40x magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

La información relacionada a la anatomía del foramen fisiológico apical es limitada. Conocer su diámetro y forma contribuye al trabajo clínico, específicamente en los procedimientos de limpieza y conformación del tercio apical. El objetivo de este estudio ex vivo fue determinar los diámetros menor, mayor y la forma del foramen fisiológico apical en las raíces de primeros molares maxilares y mandibulares. Se realizó un estudio descriptivo sobre 89 primeros molares recientemente extraídos. Se seccionaron las raíces a 3­5 mm del ápice y fueron preparadas para su análisis bajo magnificación de 40X. Se midieron los diámetros mayor y menor de cada foramen fisiológico mediante el programa Motic Images plus 2.0 ML. La forma de los forámenes fue determinada de acuerdo a la diferencia entre diámetro mayor y menor, clasificándose como redondo, oval o irregular. Un total de 174 forámenes fisiológicos fueron analizados. El promedio del diámetro menor y mayor fue entre 0,24­0,33 mm en primeros molares maxilares y entre 0,25­0,33 mm en primeros molares mandibulares. En molares maxilares, la forma del foramen más común fue la oval (50%), luego irregular (32%) y redonda (18%). En molares mandibulares, la forma oval también fue la más frecuente (59%), seguida por la irregular (23%) y redonda (18%). Los hallazgos de este estudio en relación a morfología de los forámenes fisiológicos apicales en primeros molares, permite al operador facilitar la elección de instrumentos del calibre adecuado para realizar con éxito la terapia endodóntica.

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Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

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Pese al innegable incremento en la utilización de implantes óseo integrados en el tratamiento de la extensa problemática de la desdentación parcial, la confección de prótesis removibles metálicas continua siendo a escala mundial, el principal recurso terapéutico vigente. Sin embargo, desde el punto de vista del paciente, la recuperación de la función estética es su principal falencia. Proponemos entonces, extender la utilización del principio de retención friccional inherente a la prótesis fija, mediante la preparación de "facetas retentivas friccionales" en ciertos dientes pilares, generando de este modo artificios protésicos removibles con suficiente retención, sin exhibir elementos metálicos en los sectores anteriores de la cavidad bucal. Se exponen cinco casos clínicos que respaldan la validez nuestra propuesta tras una correcta indicación (AU)

Despite the fact that nowadays the use of Osseo integrated implants is increasing worldwide nevertheless removable partial dentures with cast metal frameworks is still the most indicated treatment for cases of partial edentulism. However, patients remain reluctant regarding the aesthetic impairment brought by some of the removable partial dentures' components. Therefore we propose to apply to removable partial dentures some of the frictional retention's principles used in fixed prostheses, preparing instead of conventional guiding planes in some abutment teeth, a more wide and extensive platform what we so-called "frictional retentive facets". Accordingly we can afford to provide enough retention to our removable devices without exposing unaesthetic components such as vestibular retentive arms. Five clinical cases will be shown in order to sustain our proposal keeping in mind the need of respecting the right indication (AU)

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Thirty-two pregnant Holstein heifers weighing 499 +/- 45 kg, at 3.1 +/- .7 months of gestation and 21 +/- 2.0 months of age were confined and exposed to 30 microT magnetic fields (MFs) and a 12 h light/12 h dark light cycle. The heifers were divided into two replicates of 16 animals. Each replicate was divided into two groups of eight animals each, one group the non-exposed and the second, the exposed group. The animals were subjected to the different treatments for 4 weeks. After 4 weeks, the animals switched treatment, the exposed group becoming the non-exposed group and vice versa. Then the treatment continued for 4 more weeks. Catheters were inserted into the jugular vein, and blood samples were collected twice a week to estimate the concentration of progesterone (P4), melatonin (MLT), prolactin (PRL), and insulin-like growth factor 1 (IGF-1). Feed consumption was measured daily. The results indicated that exposure of pregnant heifers to MF similar to those encountered underneath a 735 kV high tension electrical power line for 20 h/day during a period of 4 weeks produces slight effects. This is evidenced by statistically significant higher body weight (1.2%), higher weekly body weight gain (30%), and decreases in the concentration of PRL (15%) and IGF-1 (4%) in blood serum. The absence of abnormal clinical signs and the absolute magnitude of the significant changes detected during MF exposure, make it plausible to preclude any major animal health hazard.

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Sixteen pregnant Holstein heifers weighing 521 +/- 46 kg, at 3.3 +/- 0.7 months of gestation and 2.2 +/- 2.0 months of age were confined to wooden metabolism cages and were exposed to a vertical electric field (EF) of 10.0 +/- 0.4 kV/m and an artificial light cycle of 12 h light-12 h dark. The heifers were divided into two replicates of eight each. Each replicate was divided into two groups of four animals each, one group becoming the non-exposed and the second, the EF exposed group. The exposed group were housed in metabolism cages in an area where EF were generated, and the non-exposed group, in metabolism cages located in the adjacent area where the EF was less than 2% of that present in the exposed area. The test animals were subject to the different treatments for 4 weeks continuously. After 4 weeks, the animals switched treatment, the exposed group becoming the non-exposed group and vice-versa. Then the treatment continued for 4 more weeks. Catheters were inserted into the jugular vein of the animals, and blood samples were collected on twice a week to estimate the serum concentration of progesterone (P4), melatonin (MLT), prolactin (PRL), and insulin-like growth factor-1 (IGF-1). Feed consumption was measured daily and feed samples were collected twice a week. The results indicated that exposure of dairy cattle to EF similar to those encountered directly underneath a 735 kV high tension electrical power line carrying a maximum load of current, cannot be associated with any variation in the experimental variables mentioned above. An exception to this, is the variation in MLT, which was associated with the EF exposure. Due to the inconsistency of the MLT response in the different replicates, caution should be exercised in the interpretation of this phenomenon.

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Milk production is the main agricultural income in the province of Québec, and the electrical distribution network traverses the rural dairy production region. This study evaluates the hypothesis that electric and magnetic fields may affect dairy production. Sixteen multiparous nonpregnant lactating Holstein cows (weighing 662 +/- 65 kg and with 150.4 +/- 40 days of lactation) were confined to wooden metabolic crates during the experiment with a 12:12 h light:dark cycle. The cows were divided into two replicates of eight cows each and exposed to a vertical EF of 10 kV/m and an uniform horizontal MF of 30 microT at 60 Hz. Replicate one was exposed for three periods. Each period was represented by an estrous cycle ranging from 24 to 27 days. During the first period, the electric and magnetic fields (E&MF) were off; during the second period they were on; and during the final period, they were off. The second replicate was exposed for three periods also, but the exposure protocol was reversed (first period, on; second period, off; last period, on). Exposure to E&MF (on) resulted in an average decrease of 4.97, 13.78, and 16.39% in milk yield, fat corrected milk yield, and milk fat, respectively; and an increase of 4.75% in dry matter intake.

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Survival analysis was used to study the effects of composite and descriptive linear type traits on functional herd life of Quebec Holsteins. Functional herd life was defined as the length of life from first calving to death, culling, or censoring, and was adjusted for 305-d milk production. The dataset contained information from 331,105 cows from Quebec province calving for the first time between 1981 and 1995; 58% of the records had type information. Weibull models were fitted to analyze the data. The hazard function was described as the product of a baseline hazard function and the time-independent effects of age at first calving and type, and the time-dependent effects of year of calving, stage of lactation x lactation number, annual change in herd size, 305-d milk production, and herd-year (random). Analyses were done one at a time for each type trait. The strongest relationships between survival and composite type traits were found for final score, mammary system, and feet and legs. Among the linear type traits, the highest impact on functional herd life was found for traits related to the udder.

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Survival analysis methodologies were used to study herd life in Canadian Holstein cows. Herd life was defined as true herd life or the length of time between first calving and censoring. True herd life adjusted for 305-d milk production was defined as functional herd life. Lifetime record (censored or completed) were from 331,147 Holstein cows registered in the Programme d'Analyse des Troupeaux Laitiers du Québec (PATLQ) that calved for the first time between March 1, 1981 and March 31, 1995. The Weibull (proportional hazards) model used to analyze true herd life and functional herd life contained a Weibull baseline hazard function and the time-dependent effects of year of first calving, lactation number by stage of lactation, annual change in herd size and herd-year (random), and the time-independent effects of the milk recording option (supervised or not) and age at first calving. The model for functional herd life included also the time-dependent effect of herd-year-parity class of 305-d milk production. Genetic differences between sires with regard to the hazard function of their daughters was clearly demonstrated. The hazard rate followed a different pattern in later lactations, particularly in the first 240 d in milk. Older age at first calving was found to be associated with higher risks of culling. Changes in herd size had a small impact on the hazard function of animals. The hazard decreased as production of the cow increased. Heritability in the log scale was 0.09 for true herd life and 0.08 for functional herd life, but when heritability was expressed on the original scale, the estimates for the two traits were 0.19 and 0.15, respectively. The difference in the median survival between a bull with an estimated transmitting ability of 0.6 and another bull with an estimated transmitting ability of 1.3 was 690 d or 1.7 lactations. Rank correlations between the official estimated transmitting abilities for true herd life and functional herd life and those obtained in this study were 0.62 and 0.66, respectively.

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Neutrophil phagocytic parameters, measured on 25 AI Canadian Holstein bulls, were investigated for evidence of association with production and type traits, SCC, and survival of dairy cows. An animal model and REML methodologies were used to evaluate the bulls for their neutrophil potential phagocytic activity and capacity. A total of 42,103 first lactation records, collected from 1985 through 1993 for 2919 Quebec dairy herds, were used to obtain EBV for SCC and log SCC for 697 sires. From the same population of cows, 32,900 lactation records were used to calculate EBV for survival after first lactation for 338 sires. Correlations of EBV for SCC and log SCC with all other traits were not significant. Official Canadian ETA for type traits related to the mammary system tended to be positively correlated with phagocytosis parameters. Official Canadian ETA for production traits tended to be negatively correlated. The ETA for milk protein had a significant negative correlation with potential phagocytic activity. Survival after first lactation was significantly associated with ETA for dairy character, milk fat, and fat percentage.

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The function of neutrophils within the mammary gland was modeled in vitro to include diapedesis and phagocytosis. The bovine mammary cell line, MAC-T3, provided a mammary epithelial monolayer for use as a biologically meaningful barrier to neutrophil diapedesis. Features included characteristic transepithelial resistance, tight junctional complexes, and polarity. Continuous readings of transepithelial resistance indicated a stable resistance over several hours. Staphylococcus aureus, at concentrations of 1 x 10(7) and 2 x 10(9) cfu/ml, did not appear to have any deleterious effects on monolayer integrity over short-term (1 to 2 h) exposure. Neither resting nor challenged neutrophils caused short-term damage to the monolayer. Transepithelial resistance of the monolayers remained unchanged even as neutrophils were actively migrating through the monolayer. Further work using the MAC-T3 cell line and electrical resistance to assess cell monolayer integrity could provide much insight into the mechanisms underlying degeneration of mammary epithelial cells. The ability of neutrophils to phagocytose foreign particles is important for protection of the mammary gland. Neutrophils from proven bulls varied in their rate and capacity of phagocytosis. Correlations between neutrophil function and production traits were negative and small. In vitro analysis of neutrophil function provides another tool for the study of natural mastitis resistance.

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Genetic and phenotypic correlations were estimated between 6 lifetime production and 28 linearized type traits using REML. The data set contained 34,322 cows, each with a record for all 34 traits. The analyses accounted for the fixed effects of herd, year-month, classifier, age at first calving, and stage of lactation. Heritabilities were low for lifetime traits and moderate for most type traits except stature, size, capacity, thurl width, and pin setting, which had high heritabilities. Most phenotypic correlations between lifetime production and type were in the range of .15 to .20 except for capacity, rump, and feet and legs, which were around .07. Genetic correlations were strong between lifetime production and angularity (.44 to .55) and dairy character (.53 to .56). Genetic correlations were low to moderate between life-time production and stature (.14 to .25), size (.07 to .18), texture (.19 to .26), style (.11 to .27), head (.15 to .23), pin setting (.10 to .16), rear udder (.19 to .25), and rear attachment (.10 to .22). The only notable negative genetic correlations were lifetime production with rear heel (-.16 to -.27), thurl width (-.18 to -.24), and fore udder (-.05 to -.11).

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Repeatabilities and heritabilities of days to first service, days open, and number of services per conception were estimated from 235,589 records on 80,333 Holstein cows, daughters of 306 sires obtained from the Quebec Dairy Herd Analysis Service, by REML. The model for statistical analyses included herd-year-season as a fixed effect and sire, cow (sire's daughter) within sire, and error as random effects. Variance components corresponding to sire, cow within sire, and error were then estimated by REML. Heritability estimates, obtained from the sire variance component, were .03, .05, and .03 for days to first service, days open, and number of services per conception, respectively. Repeatability estimates, obtained from the sire and cow within sire variance components were .08, .10, and .07 for days to first service, days open, and number of services per conception, respectively.

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A total of 545 milk samples were collected from 53 Holstein cows for 1 yr. On test day, morning milk yields were recorded; milk samples were analyzed for N-acetylneuraminic acid, protein, fat, casein, kappa-casein, and SCC. the relationship between the degree of glycosylation of kappa-casein and morning milk yield and composition was investigated. Data were analyzed using least squares procedures with a model that included test day, parity, stage of lactation, SCC, and phenotype for kappa-casein as fixed effects and N-acetylneuraminic acid content of kappa-casein as covariate. After adjustments were made for effects of environmental and genetic factors, the degree of glycosylation of kappa-casein was associated with morning milk yield, protein, and casein content. Milk yield increased linearly with an increase of N-acetylneuraminic content up to approximately 70 micrograms/mg of kappa-casein.

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Type information collected by the Holstein Association of Canada was combined with calving ease data from the Quebec Dairy Herd Analysis Service. Type traits considered were overall score, general appearance, dairy character, capacity, rump, rump thurl width, rump pin setting, and set of rear legs. Calving ease was considered as a direct effect and as a maternal effect in both heifers and adult cows. After editing there were 24,618 type records, 47,023 direct effect calving ease records, and 37,068 maternal effect calving ease records from 107 sires in the analyses of heifer data. there were 26,996 type records, 16,4726 direct effect calvin ease records, and 45,261 maternal effect calving ease records in the analyses of calving involving adult cows. Multiple-trait REML was used to estimate genetic correlations between calving ease and type. The heritability of calving ease in heifers was approximately 4%, for both the direct and maternal effect, and in adult cows was approximately 1.5%. Heritability of the type traits ranged from 4 to 45%. There was a tendency for the genetic correlations between type and the direct effect of calving ease to be opposite in sign to the genetic correlations between type and the maternal effect of calving ease and for the absolute value of the correlations to be lower in adult cows than in heifers.

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Heritabilities of, and genetic and phenotypic correlations between, type traits and the arithmetic mean of lactational SCC were estimated using minimum norm quadratic unbiased estimation and two multitrait REML methods. Three sets of data were analyzed. Heritabilities of all traits were small. For SCC, heritabilities varied between .09 and .11 and for type traits, between .08 and .14. Genetic correlations between SCC and type traits varied between -.22 and .30. Phenotypic correlations were very low. In general, correlations indicate a rather favorable association between SCC and udder conformation traits; that is, a desirable score on type would be associated with low SCC in milk.

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Genetic and phenotypic correlations between milk yield, fat (yield and percent, protein (yield and percent), and somatic cell count in first lactation Holstein cows were estimated using a multivariate restricted maximum likelihood algorithm. There were 18,189 daughters of 257 sires in 928 herds. Genetic correlations between pairs of yield traits were all positive (.73 to .88), but phenotypic correlations with somatic cell count were small and negative. Genetic correlations between somatic cell count, and fat percent, and protein percent were negative, -.11. Milk yield, fat yield, and protein yield had heritabilities of .36, .38, and .25.

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